Etching apparatus



Aug. 29, 1939. A. HOLMSTROM 2,171,474

ETCHING APPARATUS Filed April 17, 1935 V 3 Sheets-Sheet l zww f Aug. 29, 1939. A. HOLMSTROM 2,171,474

ETCHING APPARATUS Filed April 17, 1935 5 Sheets-Sheet 2 INVENTOR Hair/2 65%.

1939. A. HOLMSTROM 2,171,474

ETCHING APPARATUS may I INVENTOR tamed Aug. 29, 1939 'r F F i c lE'liNG APPARATUS Application April it, 1935, Serial No. 16,901

12 Claim.

This invention relates to etching machines and, more particularly, to spray-type machines in which a spray of the etching fluid is cast over metal plates or objects to be engraved. The

Ii principal object of the invention is to provide an improved machine of this character which embodies certain novel features that mark the device as a distinct improvement over prior devices of the same class.

Another object of the invention is to provide a spray-type etching machine which is adapted to function more efliciently than prior devices of this class and which is designed to enable replacement of the plates or objects to be etched 5 while the machine is running, thereby effecting a material saving in time.

A further object of the invention is to provide an etching machine of this character which is designed for maximum safety to the operator 20 and which substantially prevents injury to the operator from the gases and acid spray of the etching fluid.

Other objects and features of the invention will beapparent hereinafter.

In the accompanying drawings:

Fig. 1 is a sectional view taken longitudinally or axially of the machine;

Fig. 2 is a sectional View taken transversely of the machine;

Figs. 3 and 4 are detail sectional and face views, respectively, of the fluid-draining means employed in the machine;

Fig. 5 is a fragmentary sectional view along line 55 of Fig, 2;

Fig. 6 is a fragmentary enlarged sectional view of one of the bearing structures of the machine;

Fig. 7 is a face view of the bearing structure;

Fig. 8 is a fragmentary sectional view of a modified form of bearing structure;

Fig. 9 is a; fragmentary sectional view along line 9-9 of Fig, 8;

Fig. 10 is a 'transverse section of a modified form of the machine; 7

Fig. 1 1-is' .a fragmentary section illustrating a 45 modification;

Figs. 12.and-13 illustrate a certain form of paddle; and

Figs. 14 to 16 illustrate plate-holding devices. Referring particularly to Figs. 1 and 2 of the 50 drawings, the machine there shown comprises a housing or casing l in which there is provided a fluid reservoir 2 for the etching fluid. A shaft 3 "extends through the casing or housing and is rotatably supported by the bearing members 4 55 at the opposite ends of the housing. The shaft 3 carries paddles 5 which serve as a spraying means and are adapted to throw the etching fluid in a spray against the plate or object to be etched. The paddle shaft 3 may bedriven from any suitable source, this being accomplished in the illustrated machine by the motor 6 which is beltconnected to the shaft.

The paddles 5 making up the paddle assembly preferably take the form illustrated, each paddle comprising diametricaly-opposed blades having saw-tooth edges or edges in different angular positions which serve to break up the etching fluid into particles and, at the same time, require relatively small power consumption by virtue of their construction. The blades are preferably set in different angular positions, as illustrated. A sectional paddle of this structure has the advantages set forth in my prior Patent No. 1,391,057, granted Sept. 20, 1921.

In further accordance with the invention, there is provided a float chamber 1 which is separated from the. reservoir 2 but is in fluid communication therewith by virtue of the openings 8. A float I is disposed within the float chamber and is carried by the plunger H which is slidably supported as illustrated. The purpose of the plunger-operated float is to enable the operator to raise and lower the surface level of the etching fluid within the reservoir 2. In operation of the machine, the surface level of the etching fluid will normally be below the paddles and out of contact therewith, the float at this time being in the position shown at the top of the float chamber. Under such conditions, the paddle may rotate without affecting the etching fluid. This permits the operator to insert or remove the objects being etched or to perform any other operation while the machine is running. When it is desired to effect the etching operation, the operator may press the plunger ll so as to submerge the float H] to any desired depth within the etching fluid in the float chamber. The displacement of fluid caused by the submerged float will cause the surface level of the fluid in the reservoir 2 to rise until it is brought into cooperative relation with the paddles and the etching operation is thus effected.

There is also provided by the invention means in the form of screw jacks I! for tilting the machine either to bring the surface level of the etching fluid into cooperative relation with the paddle or to facilitate draining of the fluid through the draining means l3, which will be described in detail later. The screw jacks l2 are arranged in the base 14 supporting the machine and serve, together with the stationary members l5, as supporting feet. It will be seen that the base may be tilted toward the left, as viewed in Fig. 2, about the stationary feet i5 as a fulcrum for either of the' purposes above mentioned. Of course, any other suitable tilting means may be employed.

In further accordance with the invention, there is provided a removable accelerator battle it disposed below the paddle and having its lower edge abutting against the stop I I and its upper edge resting against the housing wall at l8. This baflie facilitates the scooping up of the etching fluid and increases the ejection speed of the fluid particles. The baflle may be provided with openings l9 and has its upper portion curved in conformity with the paddle as shown clearly in Fig. 2. This bailie may be replaced by others of the same general nature and adapted for'the same general purpose but of different specific design. The step-like structure of the stop I! provides alternative positions for the lower end of the baiiie or others replacing the same.

Above the paddle, there is provided a second baille or secondary spreader 20 which is removably supported upon the brackets 2|. These brackets serve in addition to divert to the machine any fluid particles which might be hurled towards the bearing openings, thereby preventing the escape of fluid through those openings. The baffle 29 may be provided with air passages 22 through which cooling air may be drawn into the machine. The arrangement is such that -the passages 22 terminate at their lower side adjacent the fluid spray and at their outer side adjacent the air space 23 between the cover 24 and the housing wall. This is an important feature of the invention since the acid becomes heated, particularly in warm weather. This feature will be further described hereinafter. The baiiie itself serves to break up the fluid and forms a boiling mass in the form of'a spray and directs the spray in the desired direction. In this case also the baiiie may be varied as to its details.

A removable support 25 is adapted for positioning similarly to the baffle IE but on the opposite side of the stop IT. This support has projections 26 and 21 which serve to seat the plate or object 29 to be etched and a ribbed-glass wall 29 provided by the invention. This wall serves to protect the ventilator, described hereinafter, from the acid spray. By using a device such as shown in Figs. 14 to 16 and described later, the etching fluid may be prevented from passing down behind the plate. A fan 39, which may be driven by a belt-connected motor 3| is arranged adjacent the opening 32 behind the wall 29. An air passage 33 leads upwardly from the fan chamber to a stack or chimney leading to the outside atmosphere and serving to carry off poisonous gases, etc. The cooling of the spray above mentioned is greatly enhanced by the fan which serves to propel cooling air through the spray and about the plate 28 and wall 29. In certain cases, it will be desirable to derive the cooling air from a cooling or refrigerating device, for example, where zinc plates of large dimensions are being deeply etched with a nitric acid or like solution. As far as is known, this has not been accomplished heretofore in the same way by the use of prior devices.

At the top of the machine, there is provided a cover 34 which eliminates the necessity of having within the machine itself any rough construction with protruding parts that might catch and retain splashes of fluid which might drop down and injure the operators hands or clothing. The cover 34 is supported only at its edges which are seated in recesses of the housing wall and the cover supporting frame, as shown at 35 and 35a in Fig. 2. The cover-supporting portions of the housing walls are constructed so as to convey any splashed fluid back to the walls of the housing so that the fluid may run down the walls to the reservoir. A handle 36 in the form of a rubber mushroom inserted through an opening in the cover enables removal of the cover. A transparent plate 31 is carried by the cover-supporting frame 38 and is disposed at a suitable angle of vision to enable the operator to view the etching process and control the machine accordingly. In this manner, the operator may observe whether the fluid is being sprayed in suitable quantities against the etching plates, and where the plates are to be gradually exposed to the spray in accordance with different requirements and degree ofperfection of the line and half-tone etchings, the operator may control the machine accordingly. By varying the height of the etching fluid by means of the float it, he is enabled to graduate the volume and fineness of the spray against the plate being etched or engraved.

Referring now to Fig. 5 of the drawings, there is provided adjacent the float chamber a chamber separated from the float chamber by the wall 56 and communicating with the reservoir 2 through the openings 51 and 58. The purpose of chamber 55 is to enable constant cleansing and replenishment of the etching fluid in the reservoir 2 without completely drawing off and replenishing the fluid. To this end, the openings 51 and 58 are provided at such heights or levels that the dirt and foreign matter which accumulates upon the surface of the etching fluid in reservoir 2 will be skimmed off through the openings into the chamber 55 from whence the contaminated fluid may be drained, as will be described later. Preferably, the two sets of openings 5I'and 59 at different heights or levels are provided to enable the surface cleansing of the etching fluid at different surface levels thereof. In other words, the level of the fluid communication openings between the chamber 55 and the reservoir 2 may be raised by inserting stoppers or plugs in the lower row of openings 51 so that the openings 58 will be effective. It will be understood that any number of openings at various levels may be provided for the purpose in view.

Referring now to Figs. 3 and 4 of the drawings, there are provided at the bottom of the float chamber 1 and the cleaning chamber 55 on each side of the separating wall 56 similar draining devices,- as shown clearly in Fig. 4. The left hand draining device, as viewed in Fig. 4, enables the draining of the fluid from the reservoir 2 and the float chamber 1 in communication therewith, while the right hand draining device enables the draining of the fluid from the cleaning chamber 55. As shown more clearly in Fig. 3, each of these draining devices comprises a tapered plug 39 seated in a boss 40 of the housing wall and constantly maintained fluid-tight by the spring 4| mounted in slot 42 and having its end 42 extended into the circular recess 44 at the outer end of the plug. A non-circular recess 45, which may be square in shape, is provided in the outer end of the plug to enable turning of the same by a suitable wrench or key adapted to be inserted in the said recess. The plug is provided with an opening 46 which is adapted to align with an lllll opening 4'! in the bottom of the housing when the plug is turned to fluid-draining position. In this manner, the etching fluid may be drained off into a drain pipe or funnel 48, as shown in Fig. 2.

Referring now to Figs. 6 and 7 of the drawings, each of the bearing or end structures may take the form there shown. The end wall is formed to providea bearing housing t9 within which is seated the bearing retainer Ell. There is preferably interposed between the wall of the bearing housing and the bearing retainer to a non-corrosive sealing and a cushioning member M which is preferably formed of celluloid, although it may be formed of rubber or other materials. This member may take the form of a flanged ring or collar as illustrated, forming a cushioning seal between the bearing housing and the bearing retainer, but it might also be composed of washers or the like. It is preferred to form this member of Celluloid because this mate rial is substantially unaflfected by the acid etching fluid. This member serves to dampen vibrations, eliminate noise, and causes more quiet operation of the machine.

An axial opening 52 is provided in the end wall to accommodate the shaft; this opening being sufficiently large to accommodate also a mushroom 53', there being an annular space 54 between the mushroom and the end wall to permit the passage of any of the etching fluid that might flnd its way into the structure. An annular passage 59 at the outer end of the axial passage 54 communicates with the passage til leading back to the interior of the housing of the machine and serving to convey back to the reservoir 2 any of the etching fluid or fluid particles which might find its way to the space or passage 59.

At its inner side, theend wall is provided with concentric annular projections or heads 6! and 62 which are provided, respectively, with slots 63 and 64, these serving to convey etching fluid or particles back to the reservoir 2. The head BI is disposed within the head of the mushroom 53, while the head 62 is outside and surrounds the head of the mushroom, as illustrated. This provides a tortuous path which must be taken by the fluid in order for any of it to get into the end wall structure. The inner head 6| is shaped to provide an annular recess 55 which tends to catch any of the etching fluid or fluid particles that may find its way into the structure and to convey such fluid back to the reservoir 2 via the slotted passage 64. It will be seen that this structure serves to impede the flow of any etching fluid or fluid particles into the end wall structure and also serves to convey any of the,

fluid which might get into the said structure back to the reservoir.

In Figs. 8 and 9, there is shown a modified form of bearing structure which may be employed. In this instance, the wall of the housing isprovided with an inwardly-extending integral head 66 shaped as illustrated to provide an outer annular groove 61 and having an axialopening 68 and a passage slot 69 (see Fig. 9) leading from the said opening to the periphery. The portion of the paddle shaft extending through the opening 68 carries a sleeve 10 having successive conical portions ll forming successive annular shoulders and recesses on the peripheral surface of the sleeve, as illustrated. This sleeve is smaller in diameter than the opening 68, providing an axial passage for any fluid or fluid particles which may get into the bearing structure. The annular recess 61 will serve to catch most of the fluid and convey it back to the main body of fluid in the reservoir 2 but should some of the fluid or fluid particles get into the bearing structure, it will be conveyed back to the reservoir either via the passage 69 or the passage 60. The

annular recesses on the sleeve 10 constitutes successive stages which will tend to convey the fluid to the passage 69 but should any of the fluid proceed beyond the sleeve ill, it will be conveyed through the passage 60 back to the reservoir.

In Fig. 10, there is shown a modified form of the machine in which the float chamber 1a is behind the plates 28 and 29 and the air passage 33a with its fan 30a is positioned on the opposite side of the machine behind the paddle structure. The support 25a is provided with openings for the passage of air as illustrated and, in this instance, the air flows into the upper part of the float chamber and through the said openings and the fluid spray to the air passage 33a, as illustrated by the arrows, cooling the plates 28 and 29 and the spray. The fan 30a serves to propel the air. The accelerator hafiie Ilia is in this instance integral with the housing and defines a small chamber 12 which communicates with the reservoir 2a via the openings 13. An air inlet opening 14 is provided above the level of the etching fluid and leads into the chamber 12. The purpose of this opening is to enable the use of controllable air pressure to adjust the height of the etching fluid level in lieu of the float illa. Thus, by connecting a source of controllable compressed air to the inlet port 14, the height or level of the etching fluid in the reservoir 211 may be controlled in accordance with the applied air pressure. The accelerator baffle 20a serves the same purpose as the corresponding baffle in the machine above described. It will be noted that in this modified form of the device, the cover and view plate are modified, in this instance, the cover 34a sloping upward toward the center of the machine, while the view plate or window 31a slopes downward more or less below the cover.

In Fig. 11, there is shown a modification of the lower left hand corner of the machine as viewed in either Fig. 2 or Fig. 10, in this instance, the accelerator bafile lib has air openings or passages 15 which communicate with openings I6 leading from the chamber 11. Thus, in this case, air may be drawn into the device and through the acid spray at the rear of the paddle structure.

In Figs. 12 and 13, there is shown a form of paddle which may be used in the machine and which is preferably employed in the machine shown in Fig. 10.. This paddle has portions 18 of its diametrically-opposed blades cut away or formed to provide a different angle of the blade at these portions than at the portions I9. It will be seen also from Fig. 13 that the portions 18 on one blade of the paddle are directly opposite the portions 19 on the other blade of the paddle and vice versa. The effect of this paddle structure is to give a desired uniform spray over a certain angle defined by the angular difference between the portions 18 and 19, as illustrated in Fig. 10. Furthermore, with reference to each paddle making up the paddle assembly the diametricallyopposed blades of the paddle act difierently and alternatively as will be seen from the structure shown in Fig. 13. It will be understood that any number of paddles may be employed in a particular paddle assembly and the blades may be arranged in different angular positions about the shaft as in the device of Figs. 1 and 2.

As above mentioned, a device such as those illustrated in Figs. 14 to 16 may be employed. In Fig. 14, there is shown a flexible or. resilient device 80 which is preferably formed of rubber' and which comprises vacuum cups 8| and 82 adapted for attachment respectively to wall 29 and the plate or object 28. By virtue of the adherence of the vacuum cups to the plates, these members are held firmly together, preventing the passage of etching fluid behind the plate 28. The attaching device 80 is substantially unaffected by the acid because it is formed of acidresisting material. When it is desired to remove the plate 28, the attaching device may be removed simply by exerting enough force to break the vacuum in the cups 82. I

In Figs. 15 and 16, there is shown an attaching device 83 which may be formed of rubber having vacuum cups 84 for attachment to a crystal-glass-wall 29 and having on its opposite face differently shaped vacuum cups or recesses 85 and 86 for attachment to the plate or object 28. The lower edge of the etching member may be formed as illustrated to seat the plate or object 28. In this manner, the supporting and attaching device 83 for the plate or object to be etched is interposed between the plate and the wall 29, thus eliminating entirely any adherence of these members. At the same time, the plate or object 28 is held firmly in position and a seal is effected, preventing etching fluid from passing behind the plate or object being etched and eliminating the necessity of protecting the back side of the plate.

It will be seen that the machine provided by this invention is completely acid-retaining and fully protects the operator from poisoning or other injury by the acid fluid. Moreover, by reason of the fluid level-raising feature and the normal low level of the fluid, the operator is protected against the danger incident to accidental starting of the machine and, in fact, the machine may if necessary be continuously operated as above described, it being ineffective to cause any injury as long as the float is not operated. This and the other features above described enable the attainment of the desired objects and constitute the device a distinct improvement over prior devices.

It will be obvious that various changes and modifications of the machine are possible. For example, more than one plunger-operated float might be employed. Various other modifications will occur to those skilled in the art and are to be considered within the scope of the invention.

I claim:'

1. In a spray-type etching machine, a reservoir for the etching fluid immovably disposed relative to the other parts of the machine, fluid-spraying means arranged for cooperation with the fluid in the reservoir, and means for raising and lowering the level of the fluid relative to said fluidspraying means to adjust the fluid level in relation to the fluid-spraying means and thereby adjust the fluid spray.

2. In a spray-type etching machine, a reservoir for the etching fluid, fluid-spraying means arranged for cooperation with the fluid in the reservoir, and means for varying the surface level of the fluid relative to said fluid-spraying means by regulable submersion in the fluid of a fluiddisplacement member.

3. In a spray-type etching machine, a reservoir for the etching fluid, fluid-spraying means arranged for cooperation with the fluid in the reservoir, and means comprising a plunger-responsive float for varying the surface level of the fluid relative to said fluid-spraying means by regulable submersion inthe fluid of said float.

4. In a spray-type etching machine, a reservoir for the etching fluid, fluid-spraying means arranged for cooperation with the fluid in the reservoir, a float chamber in communication with said reservoir, and a plunger-responsive float in said chamber for varying the surface level of the fluid relative to said fluid-spraying means by regulable submersion in the fluid of said float.

5. In a spray-type etching machine, fluidspraying means, a reservoir containing etching fluid immovably disposed relative to the other parts of the machine, the surface level of said fluid being normally below said means and free of contact therewith, and means for bringing the surface level of the fluid at will into cooperative relation with said fluid-spraying means.

6. In a spray-type etching machine, fluidspraying means, a reservoir containing etching fluid, the surface level of which is normally below said means and free of contact therewith, and means comprising a regulable float for raising the surface level of the fluid at will into cooperative relation with said fluid-spraying means.

7. In a spray-type etching machine, fluidspraying means, a reservoir containing etching fluid, the surface level of which is normally below said means and free of contact therewith, and means for tilting the machine to bring the surface level of the fluid at will into cooperative relation with said fluid-spraying means.

8. In a spray-type etching machine, fluidspraying means, a reservoir containing etching fluid, the surface level of which is normally below said means and free of contact therewith, and means comprising jacking elements for tilting the machine to'bring the surface level of the fluid at will into cooperative relation with said fluid-spraying means.

9. In a spray-type etching machine, a reservoir for the etching fluid, fluid-spraying means arranged cooperatively with the fluid in the reservoir, a concave baflle located below said spraying means in cooperative relation therewith, a second baflle located above said spraying means in cooperative relation therewith, said second baffle having air passages arranged cooperatively with the fluid spray to admit thereto or expel therefrom cooling air, means for supporting a plate to be etched in the path of said spray, a crystal-glass wall against which said plate may rest to protect the back of the plate from corrosion, and air-propelling means behind said wall arranged to propel air around the wall.

10. In a spray-type etching machine, a reservoir for the etching fluid, fluid-spraying means arranged for cooperation with the fluid in the reservoir, means for tilting the machine, and means comprising a manually operable fluid-displacement member for varying the surface level of the fluid relative to said fluid-spraying means.

11. In a spray-type etching machine, the combination of a container, a reservoir chamber in said container for the etching fluid. rotatable spraying means disposed in said chamber in cooperative relation with the etching fluid therein, a float chamber in communication with said reservoir chamber, a float in said float chamber for controlling the level of the fluid in said reservoir chamber, a fluid cleaning chamber arranged cooperatively with the aforesaid chambers, and fluid-draining means arranged cooperatively with said chambers,wherebytbe fluid may be drained in the path of the spray, a crystal-glass wall from said chambers. azainat which said plate may rest to protect the 12. In a spray-type etching machine, a reserback of .the plate from corrosion, and air-provoir for the etching fluid, fluid-spraying means p i nc meanaarranz d to pr p a t u sa d 5 arranged cooperatively with the fluid in the reaerspray n flmundthe wall.

voir, means for su orting a plate to be etched Am. noms'mbm. 

